1. Field of the Invention
This invention relates to an image reading apparatus for converting an image of an original into an electrical signal and reading the same. More particularly, it relates to an apparatus of the type which uses a one-dimensional image sensor such as a CCD (charge coupled device) or a photodiode array as image reading means and which reads the image by primary-scanning and secondary-scanning the image by the one-dimensional image sensor.
2. Description of the Prior Art
As a specific example of the image reading apparatus of this type, there is schematically shown in FIG. 4 of the accompanying drawings the construction of an apparatus for reading and processing any required frame image information in a roll of microfilm. Description will hereinater be made with this apparatus taken as an example.
In FIG. 4, letter F designates a roll microfilm. The roll microfilm F is wound on a rewind reel 2 and the leader tape portion thereof is wound on a take-up reel 1 manually or by an auto-loading and automatic winding mechanism (not shown). The take-up reel 1 is rotatively driven clockwise by a motor M1 and the film F is successively taken up from the rewind reel 2 onto the take-up reel 1. The film movement in this direction is forward feeding a. The rewind reel 2 is rotatively driven counter-clockwise by a motor M2 and the film F is successively rewound from the take-up reel 1 onto the rewind reel 2. The film movement in this direction is reverse feeding b.
C designates individual frame images successively photographed and recorded on the surface of the film F along the length thereof, and m denotes frame counting marks formed at the edge positions of the film which correspond to those individual frame images.
Reference numeral 3 designates a film frame illuminating projection optical system disposed between the film rewind reel 2 and the film take-up reel 1 and comprising an illuminating lamp 4, a condenser lens 5, a mark detecting sensor unit 6, an imaging lens 7, etc. L denotes an optical axis, reference numeral 8 designates a film frame illuminating position, and C' denotes an imaging plane of the frame image C positioned at the illuminating position by the imaging lens 7.
Reference numeral 9 designates a one-dimensional image sensor such as a CCD image sensor or an MOS image sensor for primary-scanning and secondary-scanning the imaging plane C' and reading the formed image on the imaging plane C', i.e., the film frame information.
This one-dimensional image sensor 9 is mounted and held on a holding member 10 with the lengthwise direction thereof, which is the primary scanning direction, parallel to the horizontal direction X--X of the imaging plane C' (the forward and reverse feeding directions of the film F).
The holding member 10 is vertically slidable along a pair of left and right vertically extending guide rails 13, 13 disposed on a base bed 11 in parallelism to the vertical direction Y--Y of the imaging plane C' (the direction perpendicular to the forward and reverse feeding directions of the film F) through brackets 12, 12. Reference numerals 14 and 15 designate a driving pulley and a driven pulley, respectively, disposed on the lower portion and the upper portion, respectively, of the base bed 11, and reference numeral 16 denotes an endless wire passed over the pulleys 14 and 15. A part of the wire is connected to the laterally projected lug 10a of the holding member 10. The driving pulley 14 is rotatively driven in the forward and reverse directions by a reversible motor M3. By the driving pulley 14 being rotatively driven in the forward direction, the wire 16 is moved round counter-clockwise and the holding member 10 for the one-dimensional image sensor 9 is moved downwardly along the rails 13, 13. Conversely, by the driving pulley 14 being rotatively driven in the reverse direction, the holding member 10 is moved upwardly along the rails 13, 13. The holding member 10 is normally held at its home position in which it is raised up to the upper ends of the rails 13, 13. In this state, the one-dimensional image sensor 9 is positioned at or slightly above a position substantially coincident with the upper side edge of the imaging plane C'. With the downward movement of the holding member 10, the one-dimensional image sensor 9 is moved down from the upper side to the lower side of the imaging plane C' along the imaging plane C' with its light-receiving surface being just coincident with the imaging plane C'.
When a required film frame image number (address) is designated and input to a control circuit by means of an operating board (console), not shown, and a search key is depressed, the driving of the motor M2 or the motor M1 is started and the forward feeding a or the reverse feeding b of the film is effected, whereby the individual frame images C of the film F successively pass the frame image illuminating position 8 of the optical system 3 in the direction of forward feeding a or the direction of reverse feeding b. In the course of this passage, the marks m of the individual frame images C are successively photoelectrically read by the mark detecting sensor unit 6, and the successive reading signals of the marks m are counted (addition-counted or subtraction-counted) by the counter of a control circuitry, not shown, and the count content is compared with the aforementioned designated and input required frame image number by a comparing circuit. When the two contents are coincident with each other, that is, when the frame image corresponding to the designated and input required frame image number becomes positioned at the frame image illuminating position 8 of the optical system 3, a stop signal is produced from the comparing circuit to a drive control circuit and the forward feeding a or the reverse feeding b of the film F is immediately stopped. That is, the required frame image is automatically searched at the frame image illuminating position 8 of the optical system 3 and held in a stationary state, and the image of that frame image is formed as a stationary image at the position of the imaging plane C'.
On the other hand, when a reading command button is depressed after the termination of said automatic searching of the required frame image, the forward driving of the motor M3 is started and the holding member 10, namely, the one-dimensional image sensor 9 is moved downwardly from the upper side to the lower side of the imaging plane C'.
Thus, the formed image on the imaging plane C', i.e., the film frame image, is linearly primary-scanned in the image widthwise direction X--X by the primary scanning function along the length of the one-dimensional image sensor 9 and also is secondary-scanned by the downward movement of the sensor 9 along the image lengthwise direction Y--Y and is photoelectrically read as a time-serial electrical picture element signal by the sensor 9. The sensor 9 terminates its reading of the entire image by downwardly moving for secondary scanning to the lower side of the imaging plane C' and, at that point of time, the motor M3 changes to its reverse revolution driving, and by the upward movement of the holding member 10 resulting therefrom, the sensor 9 is returned to its initial home position which is adjacent to the upper side of the imaging plane, and stands by until the next image reading is started.
The time-serial electrical picture element signal as the image reading signal put out from the one-dimensional image sensor 9 is input to an image reproducing apparatus, not shown, and the reproduction of an image corresponding to the read image is effected by a CRT (cathode ray tube) display, a liquid crystal display or a printer (such as a laser beam printer or an ink jet printer) is effected.
Now, the microfilm F has its individual frame images C photographed and recorded thereon in a vertically facing mode as shown in FIG. 5A or 5C of the accompanying drawings or photographed and recorded thereon in a horizontally facing mode as shown in FIG. 5B or 5D of the accompanying drawings.
The aforedescribed image reading apparatus of FIG. 4 is for use with a roll of microfilm in the vertically facing image mode, and as long as the film F in use is in the vertically facing image mode, the primary scanning and secondary scanning reading of the frame images of the film by the one-dimensional image sensor 9 is effected from the top side of the frame to the bottom side and the image reproduction by a CRT display, a facsimile apparatus or a printer is effected in the vertically facing image mode without any problems, but where the film F in use is in the horizontally facing image mode, the primary scanning and secondary scanning reading of the frame images of that film by the one-dimensional image sensor 9 is effected with one side edge of the image as the top of the scanned area and with the other side edge of the image as the bottom. This has led to the following problems:
(1) The reproduced images on the CRT display or the printer face vertically and are very difficult to see; and
(2) The primary scanning direction dimension (X--X direction dimension) W of the imaging plane C" of the frame image in the horizontally facing mode is great relative to the primary scanning length dimensional l (FIG. 3) of the one-dimensional image sensor 9 and therefore, the portions .alpha..sub.1 and .alpha..sub.2 of the imaging plane C" are outside the reading range of the one-dimensional image sensor 9 and in many cases, the reproduced image becomes imperfect at the top and bottom thereof and thus is inaccurate and useless.